I think mods are a long term advantage when you get good ones. (This is dependent on if/how they implement 6/7 dot mods)
But no, mods do not "buy you a win".
You can take a unmodded Han Solo into a team to get that initial stun and use that tactic to win a match if your toons and mods dont quite match up. Yes you would do better with good mods, but there are times where strategies will help you overcome an opponent more often than not.
Great mods can help you overcome a mirror match, but you dont always need to, that's part of the strategy in game.